We have used the methods of behavioral neurophysiology to study two major divisions of the frontal lobe of primates. the premotor cortex (PM) and the prefrontal cortex (PF). We have just published the first phase of a study on motor learning by showing that PM cells dramatically change their activity while monkeys learn what motor act to execute on the basis of an arbitrary sensory stimulus. The ability to switch the behavioral significance of sensory stimuli in the short term underlies the flexibility that characterizes the adaptation of advanced mammals to a rapidly changing but partially predictable environment. In addition, there has long been a need for more powerful behavioral methods with which to distinguish neuronal activity related to sensory and perceptual processes from those involved in the selection and control of behavior. To this end we have developed two novel behavioral paradigms that distinguish sensory from motor activity in PM and PF neurons. Our results support the hypothesis that PM plays a role in retrieving from motor memory the movement that needs to be made on the basis of a sensory event, but that PF is more involved in spatial analysis and other aspects of sensory information processing.